ZRX Series: What is the DSP switch for? The DSP switch offers three EQ presets that control the performance of the ZRX-S15P or ZRX-S18P. Product: ZRX Series Related articles ZRX Series: How do I use the phase switch? How to Change a Fuse SDJ-4000: How do I update firmware? [PA-SYS15] HOW DO I CONNECT MY SPEAKERS TOGETHER? GSYS-2400/4800 Q: What is "X Drive"